This invention relates generally to the allocation of mobile identification numbers (MIN) and, more particularly, to a system in which MINs are re-used efficiently in a cellular or wireless application environment.
The North American Cellular Network provides a ubiquitous wireless communication network designed to serve the needs of wireless voice communications. ANSI/EIA/TIA-552-1989, the Electronic Industries Association""s specification xe2x80x9cMobile Station-Land Station Compatibility Specificationxe2x80x9d describes the technical requirements for a mobile station to ensure compatibility and the ability to obtain service in any Advanced Mobile Telephone System (AMPS) cellular system. This specification formalizes basic radio requirements (modulation-type, frequency range and stability, output power) call processing procedures, and the format of messages transferred between land and mobile stations for the system currently deployed throughout North America.
Each AMPS mobile telephone has two values associated with it: a MIN and an Electronic Serial Number (ESN). The ESN is a 32-bit value programmed into the telephones""s internal software at the factory and is not adjustable. The MIN is a standard 10-digit telephone number assigned by the cellular carrier associated with a specific ESN when the telephone is sold or activated. The AMPS specification provides for a globally unique, 10-digit MIN to be associated with every mobile communication device using the system. The MIN global identifiers are managed according to the Numbering Plan Area (NPA) and individually administered by the various cellular carriers. The number space of nearly 1,000,000,000 numbers is allocated by the NPA governing body in blocks to the interested parties, such as telephone companies and cellular providers. When a mobile call is made, the cellular telephone transmits its MIN and ESN to identify itself to the cellular system for billing purposes. The use of a 10-digit MIN to identify a mobile communication device has several key advantages for voice applications, such as: (1) there is no conflict with addresses used by traditional, switched circuit telephone services; (2) mobile communication devices are addressable from wired telephone services using standard dialing methods; and (3) global uniqueness permits mobile devices to xe2x80x9croamxe2x80x9d and be identified outside their xe2x80x9chomexe2x80x9d coverage area, which roaming feature is an integral feature of the AMPS cellular telephone network.
In addition to telephone service, AMPS also provides another service for the communication of small packets of data. This service is typically used for communication of data from remote, wireless devices to a customer""s facility. Also, several commercial services provide access to the cellular network infrastructure as a wireless front-end to another data network. Such access includes cellular digital packet data (CDPD), several forms of control channel messaging, and short messaging services. In many cases, these technologies are utilized in applications that are deployed only in fixed, stationary locations. These devices typically are infrequently moved, and thereby do not require temporary roaming capability. Also, these devices are commonly involved in strictly machine-to-machine communication activities, thus eliminating the requirement that the communication device be addressed directly from switched circuit telephone services. Therefore, in many cases, such devices are assigned MINs that cannot be addressed directly from standard telephone devices.
With increasing numbers of cellular telephones, pagers, machine-to-machine communication devices, and even the increasing number of families having more than one telephone line, MIN space is becoming a scarce commodity. For communication devices that do not roam and do not need to be generally addressable by each device in the public network, there is at least a possibility that the MINs assigned to them could be reused in different cellular systems. Therefore, the practice of assigning globally unique identifiers to stationary or generally stationary communication devices is an inefficient use of MIN space.
In view of the wastefulness of providing unique MINs for stationary or generally stationary devices generally operating within a single system, a method for assigning MINs to such devices that permits efficient reuse of the assigned MINs between different systems would be advantageous and desirable. Because of restrictions imposed by carriers on amounts of data that may be communicated to and from devices such as cellemetry modems, it would also be desirable if such a method provided efficient and error-resistant assignment of MINs to remote units. It would also be desirable to provide a method for reclaiming of previously assigned MINs as the assigned device is taken out of service, or out of the service area of a particular system.
The present invention, in one aspect, is a system and corresponding method supporting the re-use, between cellular systems, of MINs assigned to stationary or generally stationary devices. Such devices, for example, utilize a cellular network as a wireless front-end to another data network and are involved in machine-to-machine communication activities. The system and method are also applicable to other types of networks. A stationary or generally stationary device, e.g., a remote device such as a cellemetry modem, communicates a commissioning request to a host system that has an associated system identifier (SID). The commissioning request includes a unique serial number (S/N) assigned to the remote device and an initial mobile identification number (MIN). If the remote device has not previously been commissioned, a temporary MIN from a list of predetermined temporary MINs is transmitted; otherwise, a previously assigned permanent MIN is transmitted. If necessary, the host system transmits a permanent MIN (or a new permanent MIN) selected from a list of available MINs associated with the host system""s SID to the remote device. The transmitted MIN is thereafter used by the remote device to access the host system, until the remote device is moved from that host system or removed from service. The host system is also in communication with a remote device database, which maintains a table of S/Ns and associated SIDs and MINs.
In another aspect of the invention, the invention comprises a remote device for communicating with a host system and a corresponding method of operating the remote device. The remote device communicates a commissioning request to a host system identified by a SID. The remote device then receives a permanent MIN from the host system, stores it in a memory of the remote device, and thereafter uses the permanent MIN to identify the remote device in communications with the host system. Use of the permanent MIN may continue until the remote device is decommissioned or moved to a different area.
In another aspect of the invention, the invention comprises a method of operating a host system associated with a SID to communicate a permanent MIN to a remote device. The host system receives a commissioning request from a remote device, selects a permanent MIN from a database of available MINs associated with the host system""s SID, and communicates the permanent MIN to the remote device.
In another aspect of the invention, the invention comprises a method for re-allocating previously allocated MINs by storing a tabulation of MINs by SIDs in an available MIN database table managed with a host system. Information on at least one individual remote device is stored in a remote device database table managed by a host system. This information includes at least a currently assigned MIN, a last registered SID, an equipment serial number (ESN) and a last known switching center. Information on a MIN an ESN and a SID are received by the host system and compared with information in the remote device database table. Stored MIN and SID entries in the remote device database table are erased, and the erased information is added to the available MIN database table when the received SID information is different from the stored SID information. If the stored SID information is identical to the received SID information, the existing MIN information is preserved.
In another aspect of the invention, the invention comprises a method of establishing contact with a host system from a remote cellular device. A fixed block of temporary MINs is stored in non-volatile memory in a remote cellular device. In addition, a MIN is randomly selected and used to contact a system host.
In another aspect of the invention, the invention comprises a method of compressing data representing an assigned MIN. The method comprises establishing a base MIN, assigning a MIN, and encoding a difference between the assigned MIN and the base MIN on a digit-by-digit basis using a tuple, with one position of the tuple representing a digit difference and another position of the tuple representing a position difference.
The above described system provides for efficient reuse of MINs in conjunction with different host systems. In addition, MINs assigned to remote devices that have moved or taken out of service are efficiently reclaimed for reuse.